Piezoelectric energy harvester/generator uses direct piezoelectric effect to convert mechanical energy to electric energy. For example, as shown in FIG. 1 (prior art), a direct piezoelectric effect may be obtained by applying pressure to a piezoelectric energy harvester/generator to light a bulb. The most familiar application of piezoelectric energy harvester/generator effect is a piezoelectric igniter as shown in FIG. 2 (prior art) where mechanical shock is converted to electricity to create a spark to ignite gas and generate a flame.
Driven by the micro, nano and green energy technologies, new developments and more applications of energy harvesting/generating devices are emerging, such as in wireless sensor networks; in military, sports and health equipment; and in communication and control devices. For instance, a wireless sensor network may contain up to thousands of sensor nodes. Replacement of batteries of sensors is therefore tiring, tedious and inconvenient, especially in harsh environments such as those facing extreme temperatures (e.g. polar regions), pollution (e.g. of air, water) and dangerous situations (e.g. volcanic eruptions). Energy harvesting collects the energy from the environment and therefore provides unlimited energy usage. A piezoelectric energy harvester is able to generate energy in the order of μW to mW, sufficient for many sensor node applications. In military applications, as the soldier needs to carry a heavy load which might induce back injuries and affect movement of the soldier, assisting walking and reducing the load (from equipment batteries) becomes necessary. Biomechanical energy harvesting is able to generate power in the order of W, which can be used to charge batteries, GPS and other equipment. In communication and control devices, to reduce the power consumption and decrease the possibility of pollution, reducing the usage of batteries is necessary. Energy harvesting devices can be used for some applications, such as TV controllers and signal transmitters.
Global demand on piezoelectric energy harvesters have been estimated at approximately US $1 billion in 2010. It is expected to grow by around 7.5-8% annually over the next few years. The total market is expected to increase to US $1.5 billion by 2015 and reach US 1.9 billion by 2018. The above data shows that piezoelectric energy harvesting has been an important area which pushes the growth of the economy.
Accordingly, governments all over the world have input large amounts of energy and resources in this area. This is led by Europe, US and Japan.
However, one of the problems that restrict the wide application of the energy harvester is the cost. PI developed a kind of DuraAct™ patch transducer. The price is SGD211 per piece. The Piezo Systems, Inc. developed another bending type piezo energy harvester. However the price is SGD274 per piece. The Face International Corporation published another Thunder type energy harvester, referred to hereafter as the Thunder transducer, which is based on a NASA invention. It is relatively cheap and may be considered an industry benchmark. However it is still more than USD100 per piece. Therefore, this work aims to develop a piezoelectric energy harvester with better performance while maintaining a low cost.